• Topic ID: id_12373438
  • Version: 1.1
  • Date: Jul 5, 2019 10:03:32 PM

CPC MNS Amplifier (5750811) Troubleshooting

Procedure Overview

Notice Image
  • warning
  • ELECTROCUTION HAZARD!
  • DANGEROUS VOLTAGES ARE PRESENT THOUGH OUT THE MULTI-NUCLEAR SPECTROSCOPY (MNS) CABINET.
  • WHEN WORKING WITHIN ANY EQUIPMENT CABINET, ENSURE THE SUBSYSTEM IS DE- ENERGIZED, AND FOLLOW ALL LOCKOUT/TAGOUT (LOTO) PROTOCOLS.

The Bird RF power measurement kit (Part# 5307511-3) is used for troubleshooting.

Use this document to troubleshoot CPC hardware failures. To troubleshoot MNS problems not specific to the CPC hardware, see MNS Troubleshooting

This document contains sections as follows:

Amplifier Diagnostics

The Status LED on the driver chassis of the CPC amplifier shows the system status of the CPC amplifier. There are also power LEDs and fault LEDs on the 2 modules.

Figure 1. CPC RF Amplifier: 3T8000MG-2 Rack Layout (Front View)

ITEM DESCRIPTION
1 LED status
2 CPC power module
3 CPC power supply

Figure 2. CPC RF Amplifier Basic Block Diagram

Reference Documents/Vendor Manuals

See these documents for additional information:

  • Operating Manual for CPC Model # 3T8000MG-2 RF Power Amplifier System (available from the online documentation library by searching for document 3T8000MG-2)

  • FRU manual, see Service Methods FRU list for MR750w or MR750 for list of FRUs

  • MNS Installation and Upgrade

  • MNS Troubleshooting

CPC Fault LED/Solution Table

In many cases, problems with the CPC amplifier are displayed through fault codes. Six status code LED indicators, labeled left-to-right 5 to 0, are on the front of the cabinet. These indicators display status and fault codes.

When the amplifier is turned on, or the AC power is cycled, the system goes through a warm-up period of approximately five minutes. If a fault happens during the warm-up period, the amplifier is forced into a Standby condition and cannot be enabled or unblanked from the MR system. In this condition, a fault message will not be reported to the MR system, but a fault condition will be displayed on the CPC fault status LEDs. You must cycle AC power to the CPC in order to reset it from the Standby condition, and restart the five minute warm-up period.

Table 1shows fault codes, a description of each fault, the recommended action and, if applicable, necessary replacement parts to overcome the fault that can be seen via the fault code LEDs.

Table 2 shows a list of problems, probable causes and solution recommendations.

Table 1 Fault Codes per Fault Code LEDs
Status Code seen at LEDs and J1 5 MSB, 0 LSB Status Code in HEX Operational LEDs Description
POWER STANDBY READY UNBLANK FAULT
000000 Hex 00 off off off off off No power to amplifier or interface disconnected.
000001 Hex 01 ON off ON off off Operational state. Ready for RF. Warm-up time has expired, ENABLE is active, and no UNBLANK command from either J1 or J2.
000001 Hex 01 ON off ON ON off Operational state with UNBLANK command from either J1 or J2.
000010 Hex 02 ON ON off off off Transient state, in warm-up. UNBLANK commands from J1 and J2 have no effect.
000011 Hex 03 ON ON ON off off Standby, ENABLE not active, and warm-up has expired. UNBLANK commands from J1 and J2 have no effect.
000100 ≡ 100000 Hex 04 ≡ Hex 20 – – – – – Not used.
100001 Hex 21 ON ON ON off ON Power supply fault.
100010 ≡ 100111 Hex 22 ≡ Hex 27 – – – – – Not used.
101000 Hex 28 ON ON ON off ON Overdrive Fault
101001 Hex 29 ON ON ON off ON Thermal Fault.
101010 Hex 2A ON ON ON off ON Peak Power Fault
101011 Hex 2B ON ON ON off ON Energy (average power) Fault
101100 Hex 2C ON ON ON off ON VSWR Fault
101101 Hex 2D ON ON ON off ON Pulse Width Fault.
101110 Hex 2E ON ON ON off ON Duty Cycle Fault
101111≡ 110110 Hex 2F ≡ Hex 36 – – – – – Not used.
110111 Hex 37 – – – – – Not used.
111000 Hex 38 ON ON ON off ON Under voltage fault
111001 Hex 39 ON ON ON off ON Over voltage fault
101011≡ 111111 Hex 3B ≡ Hex 3F – – – – – Not used.
Table 2 Troubleshooting by Symptom
Symptom Probable Cause Recommendations
Thermal fault status code

  1. Restricted air flow

  2. High ambient temperature

  3. No air flow

  1. Clean air filter

  2. Check ambient air temperature

  3. See “No air flow” symptom below
No air flow

  1. Power removed from fan

  2. Fan failure

  1. Contact your factory representative

  2. Contact your factory representative
Overdrive fault status code Excessive RF input level Reduce RF input level
High load VSWR fault status code Excessive output VSWR Check cables, tuning probe, or load
Pulse width fault status code

  1. RF pulse too long

  2. Gate pulse too long

  1. Reduce RF pulse width

  2. Reduce Gate pulse width
Duty cycle fault status code

  1. RF duty cycle excessive

  2. Gate duty cycle excessive

  1. Reduce RFduty cycle

  2. Reduce Gate duty cycle
Low RF gain (high distortion)

  1. Noise blanking signal not correct

  2. Amplifier not functional

  1. Check blanking signal timing

  2. Contact your factory representative
No RF output

  1. No input signal

  2. Faulty RF cable

  3. System fault

  4. Improper blanking

  5. Amplifier not functional

  1. Check signal source

  2. Check cables

  3. Check interconnecting cables

  4. Check blanking level polarity and connections

  5. Contact your factory representative
Power supply fault status code

  1. Wrong AC power

  2. Defective power supply

  1. Connect AC power hookup

  2. Contact your factory representative

Figure 3. Interface Connector Pin-Out Assignment

7 System States and Conditions

Operate

If the amplifier is enabled through the system interface (J1), it is in Operate mode. In this mode, the amplifier can be unblanked and used normally

Standby

If the amplifier is disabled through the system interface (J1), or the system interface connector is not sensed, the amplifier enters Standby mode. In this mode, the amplifier cannot be unblanked and the internal devices are turned off.

7.3 Fault State

If a fault occurs while the system is in the Ready state, the system enters the Fault state. In this state, the amplifier is forced into Standby mode and the fault condition is indicated. Faults are latched, so the system remains in the Fault state even if the condition which triggered it is no longer present.

Fault Reset: The system will remain in the Fault state until it receives a Fault Reset command from the system interface (J1). When the system is reset from a fault, it will go back to the Ready state if the condition that triggered the fault is no longer present. If the condition is still present, then the amplifier will remain in the Fault state even after a fault reset. The Fault Reset command has no effect outside of the fault state.

Fault Descriptions

Table 3 Fault Descriptions
Reflected power (VSWR) fault Reflected power protection is achieved by monitoring the absolute reflected power levels. A fault is generated when the level exceeds approximately one third of the rated output power of the amplifier. The circuit is disabled upon the first 1 ms of the pulse. Upon fault, the amplifier will shut down and the status code will be updated.
Overdrive fault The overdrive protection circuitry monitors the RF envelope at the output of the amplifier system. The signals are then compared using threshold comparators. If the threshold is reached, the amplifier will shut down and the status code will be updated.
Peak Power Fault The peak power protection circuitry monitors the RF envelope at the output of the amplifier system. The signals are then compared using threshold comparators. If the threshold is reached, the amplifier will shut down and the status code will be updated.
Energy fault The energy protection circuitry monitors the RF envelope at the output of the amplifier system. The circuit contains an integrator that is capable of integrating a variety of pulses at different duty cycles. This integrated signal is then compared using a threshold comparator. If the threshold is reached, the amplifier will shut down and the status code will be updated.
Thermal fault Each heat sink is provided with a bimetallic thermal sensor. In the event of an over-temperature condition, the amplifier will shut down and the status code will be updated. After sufficient time has passed to allow the heat sink to cool, the amplifier can be reset manually as described in the previous section.
Power supply fault The power supply protection circuitry monitors all auxiliary voltages and the main DC voltage supply. In the case of a fault, the amplifier will shut down and the status code will be updated. A second degree of protection is provided at the amplifier module level; see the descriptions for under-voltage fault, over- voltage fault, and over-current fault.
Pulse width fault The amplifier is equipped with envelope detection circuitry that monitors the pulse width of the RF input. The width of this envelope is compared with a pre-set threshold. If this threshold is exceeded, the amplifier will shut down and the status code will be updated.
Duty cycle fault The amplifier is equipped with envelope detection circuitry that monitors the duty cycle of the RF input. The repetition of this envelope is compared with a pre-set threshold. If this threshold is exceeded, the amplifier will shut down and the status code will be updated.
Under-voltage fault If the high current DC voltage in the system drops too low on an RF module, then the amplifier will shut down and the status code will be updated.
Over-voltage fault If the high current DC voltage in the system goes too high on an RF module, then the amplifier will shut down and the status code will be updated.
Over-current fault If an RF module is drawing excessive current, then the amplifier will shut down and the status code will be updated.
Interconnect fault "Interconnect Fault" is an obsolete fault condition that is not present in the 3T8000MG-2 amplifier system.

Troubleshooting for Low Gain

This version of CPC amp contains only one module that produces the RF Output. The only troubleshooting for this module is to confirm that there is RF output going into the Power Amplifier module using an oscilloscope, and then confirm that there is RF output coming out of the module using the RF power measurement kit.

Finalization

  1. Reset any hardware changes to return the system to normal product configuration.

  2. If components were swapped during the troubleshooting process, perform MNS Functional Checks.